- Natural formation of vinyl chloride in the terrestrial environment
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Vinyl chloride is a highly reactive and toxic substance which is widely used in industry. It is the parent compound of poly(vinyl chloride) (PVC), one of the most important industrial polymers. Until now, it was thought that vinyl chloride found in the environment is exclusively man-made or results from the degradation of other anthropogenic substances, such as trichloroethylene and tetrachloroethylene. Here, we demonstrate that vinyl chloride also has natural sources. Soil air and ambient air from a rural area in Northern Germany were investigated for volatile chlorinated halocarbons. The concentrations of vinyl chloride in the soil air were significantly enhanced as compared to ambient air, indicating a natural formation of this compound in the soil. A series of laboratory experiments using different soils and model compounds was conducted, which clearly proved that vinyl chloride could be produced during soil processes. We propose that this highly reactive compound can be formed during the oxidative degradation of organic matter in soil, for example, in a reaction between humic substances, chloride ions and an oxidant (ferric ions or hydroxyl radicals). The redox-sensitive aromatic compounds in soil such as catechols and o-quinones can be degraded to CO2, accompanied by the release of vinyl chloride and other volatile chlorinated compounds. This process could have started in the Late Silurian to Early Devonian, 400 million years ago, when the first soils on earth evolved.
- Keppler, Frank,Borchers, Reinhard,Pracht, Jens,Rheinberger, Stefan,Scholer, Heinz F.
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- Effect of preparation method on the performance of porous RuOx/Co3O4 catalysts for 1, 2-dichloroethane oxidation
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Porous Co3O4 with high yield was synthesized through calcination from plate-like Co(OH)(OCH3). Then, a series of Co3O4 supported RuOx catalysts were prepared using three different loading methods, including homogeneous precipitation (HP), precipitation-deposition (DP), and wet impregnation (IM). Their physicochemical properties were investigated by various characterization techniques, and their performance for catalytic oxidation of 1, 2-dichloroethane (1, 2-DCE) was also evaluated. RuOx/Co3O4-HP possessed the most outstanding low-temperature reducibility, more oxygen vacancies, and surface active oxygen, correspondingly exhibited a better catalytic activity and lower selectivity of polychlorinated by-products. Moreover, RuOx/Co3O4-HP also presented an excellent performance for other types of hydrocarbons abatement. The stability test showed that the RuOx/Co3O4-HP showed highly stable activity for 1, 2-DCE oxidation, and the beneficial effect of water was further confirmed.
- Deng, Wei,Gao, Biao,Guo, Limin,Jia, Ziye,Liu, Dongqi,Zhu, Simin
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- PROCESS FOR THE PRODUCTION OF ETHYLENE, VINYLIDENE, AND HYDROGEN CHLORIDE FROM ETHANE
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A process is provided for the chlorination of ethane using chlorine as the chlorinating agent to produce vinylidene (1,1-dichloroethylene), hydrogen chloride and ethylene.
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Page/Page column 5-8
(2016/06/13)
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- On the mechanism of action of gated molecular baskets: The synchronicity of the revolving motion of gates and in/out trafficking of guests
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We used dynamic 1H NMR spectroscopic methods to examine the kinetics and thermodynamics of CH3CCl3 (2) entering and leaving the gated molecular basket 1. We found that the encapsulation is first-order in basket 1 and guest 2, while the decomplexation is zeroth-order in the guest. Importantly, the interchange mechanism in which a molecule of CH3CCl3 directly displaces the entrapped CH 3CCl3 was not observed. Furthermore, the examination of the additivity of free energies characterizing the encapsulation process led to us to deduce that the revolving motion of the gates and in/out trafficking of guests is synchronized, yet still a function of the affinity of the guest for occupying the basket: Specifically, the greater the affinity of the guest for occupying the basket, the less effective the gates are in "sweeping" the guest as the gates undergo their revolving motion.
- Hermann, Keith,Rieth, Stephen,Taha, Hashem A.,Wang, Bao-Yu,Hadad, Christopher M.,Badjic, Jovica D.
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body text
p. 90 - 99
(2012/03/09)
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- Method of stabilizing trichloroethane during production
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Trichloroethane, e.g., 1,1,1-trichloroethane, is stabilized during processing at temperatures at which it is susceptible to thermal decomposition by conducting such processing in the presence of a stabilizing amount of a stable free radical stabilizer, e.g., a material having a 2,2,6,6-tetra(lower alkyl)-1-piperidinyloxy-yl free radical group such as 2,2,6,6-tetramethyl-4-hydroxy-1-piperidinyloxy.
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- Transient puffs of trace organic emissions from a batch-fed waste propellant incinerator
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Emissions data have been obtained from a waste propellant incinerator. The incinerator is a dual fixed hearth, controlled air incinerator equipped with acid gas and particulate scrubbing. Puffing has been evident in this waste propellant incinerator by spikes in the CO concentration. Transient puffs of organics may travel down the combustion chambers and lead to stack emissions. The major conclusions from this study are that (1) transient puffs are formed due to the semi-batch feed nature of the combustion process (causing a local oxygen deficiency) and high water content of the desensitized propellant; (2) in batch-fed combustors, puffs can contribute to most of the organic emissions (which are relatively low) measured with US EPA sampling and analytical methods; (3) it is estimated that batch-fed combustion contributes up to 7-18 times more emissions than steady-state combustion will generate; (4) by applying dispersion analyses to determine the amount of oxygen deficiency in the flame zone, the combustion zone concentration of CO during batch-fed operation could be as high as 160,000 ppm, compared to a measured peak stack concentration of 1200 ppm CO; and (5) an organic sample is collected and averaged over at least a 2-h period that smooths out the transient peaks of organics emissions during batch-fed operation. For emissions that are associated with long-term potential health impacts, this is an appropriate sampling method. However, if a compound has a short-term potential health impact, it may be important to measure the time-resolved emissions of the compound.
- Hart, John R.
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p. 559 - 569
(2007/10/03)
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- Reactions of chlorinated vinylsilanes with hydrogen chloride
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Catalytic hydrochlorination of a series of chloro(chlorovinyl)methylsilanes was studied. The course of the reaction depends on the number and position of the chlorine atoms in the initial monomers.
- Lakhtin, V. G.,Ryabkov, V. L.,Kisin, A. V.,Nosova, V. M.,Chernyshev, E. A.
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p. 375 - 378
(2007/10/03)
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- Kinetics of the R + Cl2 (R = CH2Cl, CHBrCl, CCl3 and CH3CCl2) reactions. An ab initio study of the transition states
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The kinetics of the reactions of CH2Cl, CHBrCl, CCl3 and CH3CCl2 radicals with molecular chlorine were investigated in a heatable tubular reactor coupled to a photoionization mass spectrometer. The reactions were studied under pseudo-first-order conditions. The radicals were photogenerated at 248 nm. The pressure-independent rate constants determined were fitted to the following Kooij and Arrhenius expressions (units in cm3 molecule-1 s-1): k-(CH2Cl) = 7.56 × 10-17(T)1.45 exp(-350 J mol-1/RT), k(CHBrCl) = 5.83 × 10-20(T)2.3 exp(-300 J mol-1/RT), k(CCl3) = (8.4 ± 2.9) × 10-13 exp[-(25 ± 9) kJ mol-1/RT] and k(CH3CCl2) = 1.10 × 10-26(T)4.3 exp(+15000 J mol-1/RT). The Arrhenius rate expression for the Cl + CCl4 reaction was determined to be k(Cl + CCl4) = (3.9 ± 3.2) × 10-13 exp[-(71 ± 9) kJ mol-1/RT] using the kinetics measured and the thermochemistry of the CCl3 radical. Errors for the Kooij expressions were estimated to be 25% overall, and for the Arrhenius expressions they were calculated to be 1σ + Student's t values. The transition states of the measured R + Cl2 and four other similar reactions were localized and fully optimized at the MP2/6-31G(d,p) level of theory by ab initio methods. The energetics of the reactions were considered by determining thermochemical and activation parameters of the reactions. The reactivity differences of the radicals studied were explained by a free-energy correlation using an electronegativity difference scale.
- Seetula, Jorma A.
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p. 3561 - 3567
(2007/10/03)
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- CH3CF3-nCln haloalkanes and CH2=CF2-nCln halo-olefins on γ-alumina catalysts: reactions, kinetics and adsorption
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The heterogeneously catalyzed reactions of the haloalkane, CH3CF(3-n)Cln, and halo-olefin, CH2=CF(2-n)Cl(n), series have been studied on a γ-alumina catalyst and the experimental results compared with calculated thermodynamic data.The main reactions occurring in this system can be explained by the following reaction paths: dehydrohalogenation, hydrohalogenation, F/Cl and Cl/F exchange with hydrogen halides.Dismutation reactions which are observed in other halocarbon series are unimportant in this system.A survey of the dominant reactions is given.In addition, the kinetic behaviour of CH3CF2Cl on the γ-alumina catalyst and the adsorption of various halocarbons have been investigated.The isosteric enthalpies of adsorption demonstrate that the interaction between the haloalkanes and the solid surface is more dominant than simple condensation. - Keywords: Chlorofluorocarbons; γ-Alumina catalysts; Heterogeneous catalysis; Kinetics; Adsorption; Enthalpy of adsorption
- Hess, A.,Kemnitz, E.
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- MECHANISMS OF FREE-RADICAL REACTIONS XXX. MECHANISM OF FREE-RADICAL CHLORINATION OF ORGANIC COMPOUNDS BY SODIUM HYPOCHLORITE IN THE PRESENCE OF PHASE-TRANSFER CATALYSTS
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The reaction of hydrocarbons and their derivatives with sodium hypochlorite in the presence of phase-transfer catalysts and also with dichlorine monoxide takes place by a common free-radical mechanism, and the hydrogen atom is abstracted both by the chloroxy radical and by the chlorine radical.In the range of pH 7-9 it is possible to conduct the free-radical chlorination process with a minimal contribution from the site processes involving oxidation and ionic chlorination of the alkyl aromatic substrates.The relative rate constants for a series of organic substrates was measured by the method of competing reactions.The observed selectivity of the process is a quantity that depends on the relative contribution from the two competing mechanisms.
- Dneprovskii, A. S.,Eliseenkov, E. V.
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p. 235 - 240
(2007/10/02)
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- THE EFFECT OF NONCOMPLEXING SOLVENTS ON THE SELECTIVITY OF THE FREE-RADICAL CHLORINATION OF 1,1-DICHLOROETHANE
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During study of the effect of noncomplexing solvents (dichloromethane, pentachloroethane, hexachloroacetone, nitromethane) on the selectivity of the photochlorination of 1,1-dichloroethane correlations for each of them were obtained between the rate constants for the abstraction of a hydrogen atom by the chlorine radical and the various positions of the substrate.These relations were compared with the analogous relations for Freon 113 and acetic acid.A satisfactory correlation was obtained between these relations and the solvent parameters.The obtained results were interpreted in terms of theories on the solvated character of the chlorine radicals.The departure of the point corresponding to acetic acid from the correlation was explained by specific interactions between 1,1-dichloroethane and the solvent.
- Aver'yanov, V. A.,Vlasov, D. V.
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p. 1521 - 1525
(2007/10/03)
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- Reaction of hypochlorites with polyoxypropylene glycols
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Polyoxypropylene diketones are prepared by initially adding predetermined amounts of a mono- or dicarboxylic acid having a pKa water solubility at 25° C. of >1%, a polyoxypropylene glycol and, optionally, water, to a reaction zone and thereafter adding an aqueous solution of an alkali metal or an alkaline earth metal hypochlorite oxidant to the reaction zone with agitation under reaction conditions including a temperature of about 10° to about 50° C., a pressure of about 0 to 1,000 psig. and a total reaction time of about 0.5 to 20 hours, whereby said polyoxypropylene glycol will be substantially selectively converted to the said corresponding diketone, and recovering said diketone.
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- A Novel Laser-induced Synthesis of 1,1-Dichloroethylene from 1,1-Dichloroethane
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The laser-induced photochlorination of 1,1-dichloroethane followed by its dehydrochlorination has been examined in a flow reactor under normal pressure at 25 - 200 deg C, which has been proved to be a novel direct synthesis of vinylidene chloride.
- Oshima, Yoshito,Iguchi, Kayoko,Tominaga, Hiro-o,Koda, Seiichiro
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p. 2101 - 2104
(2007/10/02)
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- Aluminium(III) Chloride-Chlorohydrocarbon Chemistry. Fourier Transform Infra-red Spectroscopic Studies of the Reactions between Solid Aluminium(III) Chloride and 1,1,1-Trichloroethane or 1,1-Dichloroethene Vapours
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The reactions of 1,1,1-trichloroethane and 1,1-dichloroethene vapours with solid aluminium(III) chloride have been studied using Fourier-transform i.r. spectroscopy to determine stoicheiometries as a function of time.Dehydrochlorination of 1,1,1-trichloroethane to give 1,1-dichloroethene and hydrogen chloride appears to be the only important process in the initial stage of the reaction, but the 1,1-dichloroethene formed reacts with the solid phase and the main product is a mixture of involatile chlorohydrocarbon species.The quantity of hydrogen chloride evolved indicates that the involatile material is highly unsaturated and in both reactions AlCl3 becomes progressively coated with a strongly purple-coloured tar.Small quantities of carbon tetrachloride are also produced in both reactions.
- McBeth, David G.,Winfield, John M.,Cook, Bernard W.,Winterton, Neil
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p. 671 - 676
(2007/10/02)
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- Manufacture of ketone derivatives of polyoxypropylene glycols
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Polyoxypropylene diketones are prepared by initially adding predetermined amounts of glacial acetic acid, a polyoxypropylene glycol and, optionally, water, to a reaction zone and thereafter adding an aqueous solution of an alkali metal or an alkaline earth metal hypochlorite oxidant to the reaction zone with agitation under reaction conditions including a temperature of about 10° to about 50° C., a pressure of about 0 to 1,000 psig. and a total reaction time of about 0.5 to 20 hours, whereby said polyoxypropylene glycol will be substantially selectively converted to the said corresponding diketone, and recovering said diketone.
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- Photochemistry of tetramethyl(2,2'-bipyridine)platinum(IV)
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It is shown that photolysis of using incident radiation with λ 436 or 473 nm occurs with high quantum efficiency of 0.8-1.0 to give homolysis of a methyl-palladium bond; this has allowed a study of the chemical reactions of the radical.
- Hux, Janet E.,Puddephatt, Richard J.
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p. C31 - C34
(2007/10/02)
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- 1-(substituted phosphorous)-azetidinone antibacterials
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Antibacterial activity is exhibited by 2-azetidinones having an acylamino substituent in the 3-position and having an activating group in the 1-position of the formula STR1
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- Reactivity and Intersystem Crossing of Singlet Methylene in Solution
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Evidence is reported wich demonstrates that singlet methylene, produced from the photolysis of diazomethane or diazirine undergoes intersystem crossing to form triplet methylene in perfluorohexane solvent.The results of triplet sensitized photolysis and of direct photolysis experiments with dilute concentrations of substrate (cis- and trans-2-pentene and chloroform) appear to be essentially identical.Stern-Volmer analyses of the competition kinetics between acetonitrile and 2-pentenes or chloroform for singlet methylene are consistent with the near diffusion controlled reactivity of singlet methylene.With the assumption of diffusion-controlled reactions for singlet methylene, plots of the quantum yield for singlet vs. triplet reaction for methylene allow the first estimate (-1) of the rate of intersystem crossing of singlet methylene in the condensed phase.This value is considerably smaller than the value that is extrapolated to the solution phase from results in the gas phase.The possible reasons for this difference are discussed.
- Turro, Nicholas J.,Cha, Yuan,Gould, Ian R.
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p. 2101 - 2107
(2007/10/02)
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- EFFECT OF SPECIFIC SOLVATION ON THE SELECTIVITY OF THE FREERADICAL CHLORINATION OF CHLOROETHANES
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The chlorination of 1,1-dichloroethane in the presence of the complex-forming solvent chlorobenzene was investigated.It was shown that the dilution of 1,1-dichloroethane under the conditions of a constant chlorobenzene concentration leads to a decrease in the / ratio.The results contradict the previously published view concerning the possibility of self-association in chloroethanes through the formation of hydrogen bonds and the effect of such association on the selectivity of the liquid-phase chlorination of chloroethanes.
- Aver'yanov, V. A.,Ruban, S. G.
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p. 1465 - 1466
(2007/10/02)
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- EFFECT OF ACETIC ACID ON THE SELECTIVITY OF FREE-RADICAL CHLORINATION PROCESSES
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The effect of acetic acid on the selectivity of the chlorination of 1,1-dichloroethane and 2-chloropropane in the range of temperatures between -10 and 60 deg C was investigated.It was shown that increase in the acetic concentration leads to a decrease in the amount of products from chlorination at the chlorine-substituted position, and in the region of high solvent concentrations the selectivity of chlorination becomes insensitive to temperature.The results are discussed from the standpoint of the increase in the steric and energy hindrances during attack at the more substituted positions due to the solvatation of the chlorine atoms and the substrate molecules.
- Aver'yanov, V. A.,Ruban, S. G.
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p. 2267 - 2269
(2007/10/02)
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- Kinetics of Cl(2PJ) Reactions with the Chloroethanes CH3CH2Cl, CH3CHCl2, CH2ClCH2Cl and CH2ClCHCl2
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The kinetics of the reactions Cl(2PJ) + RHCl -> RCl + HCl were investigated over the temperature range 257-426 K for RHCl = CH3CH2Cl (k2), CH3CHCl2 (k3), CH2ClCH2Cl (k4), and CH2ClCHCl2 (k5).Cl(2PJ) was produced by 355 nm pulsed laser photolysis of Cl2 and monitored by time-resolved resonance fluorescence spectroscopy.The data are adequately described by the following Arrhenius expressions (units are cm3 molecule-1 s-1, errors are 2? and refer to precision only): k2=(2.34+/-0.42)E-11exp, k3=(8.19+/-1.84)E-12exp,k4=(2.21+/-0.51)E-11exp, and k5=(4.88+/-1.41)E-12exp.Under some experimental conditions evidence for Cl(2PJ) regeneration via a secondary reaction was observed.At 258+/-1 K, deviations of Cl(2PJ) temporal profiles from first-order behavior were attributable to the reactions RCl + Cl2 -> RCl2 + Cl(2PJ)(kj).By modeling the observed C(2PJ) temporal profiles, we found the rate constant kj to lie in the range (5-12)E-14 cm3 molecule-1 s-1 for all RCl investigated.The reactivity trends observed in reactions of Cl2PJ) with C2HXCl(6-x), x=3-6, are discussed.
- Wine, P. H.,Semmes, D. H.
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p. 3572 - 3578
(2007/10/02)
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- MECHANISM OF THE SELECTIVE ACTION OF AROMATIC SOLVENTS ON FREE-RADICAL CHLORINATION. CHLORINATION OF 1,1-DICHLOROETHANE
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The effect of six solvent of aromatic nature (benzene, chlorobenzene, o-dichlorobenzene, fluorobenzene, tert-butylbenzene, nitrobenzene) on the selectivity of the free-radical chlorination of 1,1-dichloroethane was investigated.It was shown that the yield of 1,1,1-trichloroethane increases with increase in the concentration of the solvent and with decrease in the temperature.A mechanism based on the concept of the formation of ? complexes between the chlorine atom and the aromatic molecules is proposed for the selective action of the aromatic solvents on free-radical chlorination.Mathematical model agreeing with the pro posed mechanism for the selective action of the solvents were obtained for the selectivity in aromatic solvents.It was shown that the parameters of the selectivity models characterizing the capacity of the solvents for complex formation and the relative reactivity of the C-H bons to attack by the ? complexes vary in line with the electron-donating characteristics of the solvents.
- Aver'yanov, V. A.,Zarytovskii, M. V.,Shvets, V. F.,Treger, Yu. A.,Emel'yanov, V. I.
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- Photolysis of Butane-2,3-dione in Fluorocarbon Solvents; a Chemically Induced Nuclear Polarization (CIDNP) Study
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CIDNP observations of the polarized signals from products of radical reactions in solutions of neat butane-2,3-dione in perfluorocyclohexane and perfluorodecalin, and in solutions with added radical scavenger or hydrogen donor, are consistent with three primary processes.There are symmetric (probably) and unsymmetric fragmentation and hydrogen-abstraction by triplet butane-2,3-dione from the starting material, and each yields free radicals.In all solutions the mechanisms of ensuing reactions are suggested.In the presence of CCl4 and CCl3Br pair substitution effects dominate the CIDNP behaviour.When high concentrations of propan-2-ol are present evidence is given for reaction of the excited singlet state of the parent molecule.
- Broomhead, Eleanor J.,McLauchlan, Keith A.,Roe, Jonathan C.
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p. 796 - 804
(2007/10/02)
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